• Journal of Korea Foundry Society
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• v.17 no.2
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• pp.180-187
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• 1997

The influence of solidification condition on the segregation of SiC particles in the $Al-xSi/6wt%SiC_p$(x: 6, 10, 14, 18${\cdot}$wt%) composites was investigated in the study. The results are as follows: 1) During the counter-gravity unidirectional solidification of $Al-Si/SiC_p$ composites melt, most of the SiC particles are pushed to the top of the casting. 2) The SiC particles pushing in the $Al-Si/SiC_p$ composite melts are not observed, when the interface velocity of melts increases more than 1.41 ${\mu}m/sec$. 3) The SiC particles are entrapped in the interdendrite regions, when the sizes of SiC particles in the $Al-Si/SiC_p$ composites are large than ${\varphi}22{\mu}m$.

• Journal of the Korea Safety Management & Science
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• v.16 no.3
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• pp.201-207
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• 2014

This study is aimed to improve safety of ladle in the metal products manufacturing industry. Burns may occur from spills, spatters or eruptions of hot metal from ladles during pouring or transporting. According to the statistics of occupational accidents about the ladle, many victims were exposed to or contacted with extreme temperatures. The many fatal injuries occurred as a result of unexpected discharging of molten metal due to tipping over ladles. To prevent ladles from turning over, the trunnion axis shall be located below the center of gravity of the ladle at all operating condition. For this purpose, the equation is proposed to calculate the minimum location of a trunnion axis for definite static stability when tilting.

• Journal of Powder Materials
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• v.12 no.3
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• pp.208-213
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• 2005

Aluminum matrix composites strengthened by the quasi-crystalline (QC) phase were developed in the present study. The icosahedral $Al_{65}Cu_{20}Fe_{15}$ phase was produced by gravity casting and subsequent heat treatment. The mechanical milling process was utilized in order to produce the Al/QC composite powders. The microstructures of the composite powders were examined by optical microscopy (OM) and scanning electron microscopy (SEM). The composite powders were subsequently canned, degassed and extruded in order to produce the bulk composite extrusions with various volume fractions of QC. The microstructure and mechanical properties of the extrusions were examined by OM, SEM, Vickers hardness tests and compression tests. It was found that the microstructures of the Al/QC composites were uniform and the mechanical properties could be significantly improved by the addition of the QC phase.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.3
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• pp.150-158
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• 2022

The effects of scandium addition on the Al-6Si-2Cu Alloy were investigated. The Al-6Si-2Cu-Sc alloy was prepared by gravity die casting process. In this study, scandium was added at 0.2 wt%, 0.4 wt%, 0.8 wt%, and 1.0 wt%. The microstructure of Al-6Si-2Cu-Sc alloy was investigated using Optical Microscope, Field Emission Scanning Electron Microscope, Electron Back Scatter Diffraction, and Transmission Electron microscope. The microstructure of Al-6Si-2Cu alloy with scandium added changed from dendrite structure to equiaxed crystal structure in specimens of 0.4 wt% Sc or more, and coarse needle-shape eutectic Si and β-Al₅FeSi phases were segmented and refined. The nanosized Al₃Sc intermetallic compound was observed to be uniformly distributed in the modified Al matrix.

• Journal of Korea Foundry Society
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• v.34 no.3
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• pp.100-106
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• 2014

In recent years, Mg and its alloys have attracted a great deal of attention due to their low density, relatively excellent castability, and straightforward recyclability. Mg alloys have been widely applied to various industrial fields, and are representatively used in automotive and electronic parts. According to previous researches, the electrical conductivity of Mg alloys greatly decreases with increasing Al content. However, with the addition of Zn and/or Cu, the electrical conductivity of Mg alloys is maintained or slightly increased, and improved mechanical properties are obtained as well. On this basis, Mg-Zn-Cu alloys have been investigated in the present study with a focus on the effect of adding Zn and Cu on the electrical conductivity. The Zn and Cu contents ranged from 4 to 6wt.% and 0 to 1.5wt.%, respectively. Ternary Mg-Zn-Cu alloys have been prepared by gravity casting in a steel mold. In the as-casting condition, the electrical conductivity of Mg-Zn-Cu alloys showed a linear increasing trend with decreasing Zn and increasing Cu contents. Furthermore, impact values of Zn = -1.5 and Cu = 2.5 were determined for these alloys by electrical conductivity tests.

• Transactions of Materials Processing
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• v.19 no.5
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• pp.311-319
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• 2010

Rare earth metal Ce has a relatively low melting point and high specific gravity. Because of its significantly high affinity to oxygen, nitrogen and sulfur, it is highly usable as a steel refining agent. However, because Ce compound has relatively high specific gravity, it is difficult to be separated from molten steel through floatation, and it degrades the purity of molten steel, or may clog the nozzle in continuous casting. Such problem may be solved by using an appropriate deoxidation agent together with Ce and settling molten steel sufficiently after refining. Thus a fundamental study in the formation behavior of non-metallic inclusion in Ce added Hyper Duplex STS melts was investigated. The addition amount of Ce, melt temperature were considered as experimental variables. A main non-metallic inclusion in mother alloy is 51(wt%MnO) - 27.6(wt%SiO$_2$)- 10.9(wt%$Cr_2O_3$). Non-metallic inclusion was dramatically decreased and the particle size was fined as the amount of Ce increased. Moreover (%MnO) and (%SiO$_2$) of non-metallic inclusion were decreased. But (%$Al_2O_3$)were relatively increased. The number of non-metallic inclusion were decreased and the large particle size were increased by increasing the temperature of molten steel.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.2
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• pp.92-97
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• 2011

Landfill is the main treatment method for bottom-ash because it has not only an irregular particle size and ingredients but also not proper recycling treatment. The aim of this study is to raise recycling rate of bottom-ash(nonplasticity pulverulent) and for the purpose of alternatives of clay to investigate the properties of Bottom-ash (B/A)-Hard Clay (H/C) bodies with controlled interfacial chemistry properties. After investigating the sedimentation height of suspensions with controlled pH, it was discovered that there was no hetero-polar aggregation for mixed slips because hard clay and bottom-ash had similar interfacial chemistry properties. Also, bulk density, water absorption, and microstructure properties of each pellet was observed that made by silp casting method and manufactured at $50^{\circ}C$ intervals between $1000{\sim}1250^{\circ}C$. As a result, dispersed slip of clay and bottom ash are possible for slip casting and plastic forming process because they exhibit Bingham plastic behavior. Products that made by slip with dispersed clay and bottom ash are not only suitable for KS L 4201 and KS L 1001 at $1250^{\circ}C$ but it is also possible to apply for ceramic and sanitary ware because specific gravity was about 15 % lighter than general ceramic materials.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.102-108
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• 2018

The objective of this study is to develop the mechanical properties of an AlSiCu aluminum alloy using the two-step solution heat treatment. The microstructure of the gravity casting specimen represents a typical dendrite structure with a secondary dendrite arm spacing (SDAS) of 40 um. In addition to the Al matrix, a large amount of coarsen eutectic Si phase, $Al_2Cu$ intermetallic phase, and Fe-rich phases is generated. The eutectic Si phases are fragmented and globularized with the solution heat treatment. The $Al_2Cu$ intermetallic phase is also resolutionized into the Al matrix. The $2^{nd}$ solution temperature at $525^{\circ}C$ may be an optimal condition to enhance the mechanical properties of the AlSiCu aluminum alloy.

• Journal of Korea Foundry Society
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• v.24 no.5
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• pp.273-280
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• 2004

Vibrational motions of the compaction table were investigated to select the optimal operation conditions of sand filling and compaction for the EPC process. Their modes were measured at the nine points of the table with changing the relative rotation angles between the two eccentric mass vibrators which were attached parallel beneath the table. Well-defined vibration modes were measured at the center of the table but those of left and right sides of the table were distorted regardless of rotational angle differences. The distortion of vibration modes at both sides of the table were caused by the moment generated by offset positions of two eccentric masses. It was found that the uniform vibration modes would be gathered by controlling the relative distances between the rotating axis and the center of gravity in the compaction system at the various conditions of vibration modes and rotational angle differences.

• Journal of Korea Foundry Society
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• v.39 no.3
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• pp.33-43
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• 2019

In this study, the effects of Zn additions on the mechanical properties of Al-Si-Mg-Cu alloys were investigated by increasing the amount of Zn up to 8wt.%. As the Zn content was increased up to 6 wt.%, the yield strength and elongation changed linearly without any significant changes in the size and shape of the main reinforcement phase. However, it was confirmed by SEM observation that the Mg-Zn phase formed between the reinforcement phases when the amount of Zn added exceeded 7wt.%. A Mg-Zn intermetallic compound formed between the $Mg_2Si$ phase, becoming a crack initiation point under stress. Thus, the formation of the Mg-Zn phase may cause a sharp decrease in the elongation when Zn at levels exceeding 7 wt.%. It was also found that the matrix became more brittle with increasing the Zn content. From these results, it can be concluded that the formation of the Mg-Zn intermetallic compound and the brittle characteristics of the matrix are the main causes of the remarkable changes in the mechanical properties of this alloy system